What is atrial fibrillation?

Atrial fibrillation is a heart rhythm disorder that makes your heart beat irregularly and either too fast or too slow. The condition is the most common irregular heart rhythm (arrhythmia), in the UK it affects approximately one in 45 people.

If you are diagnosed with atrial fibrillation, your risk of stroke can be increased up to five times. However, your doctor can prescribe blood-thinning medications to greatly reduce your risk.

When you have atrial fibrillation, the atria (upper chambers of the heart) beat irregularly and out of sync with the ventricles (lower chambers of the heart). For this reason, atrial fibrillation can cause symptoms such as heart palpitations (a rapid, pounding heartbeat), shortness of breath, and fatigue.

While the condition itself usually isn’t life-threatening, it will require treatment to prevent any serious complications.

Atrial fibrillation occurs when the heart rhythm is irregular and either beats too fast or too slow. It is the most common arrhythmia.

Atrial fibrillation occurs when the heart rhythm is irregular and either beats too fast or too slow. It is the most common arrhythmia.

Atrial fibrillation symptoms

You might not experience any symptoms if you have atrial fibrillation. This is one of the main reasons why many people have it and yet remain undiagnosed – approximately 0.5% of the world’s population are currently living with undiagnosed atrial fibrillation.

Typical symptoms of atrial fibrillation often include:

  • tiredness – due to the heart not pumping sufficient oxygenated blood to the rest of the body
  • weakness – a result of the heart’s inefficiency caused by atrial fibrillation
  • breathlessness – during exercise, everyday activities, or even at rest
  • palpitations – you will suddenly notice your heart beating strongly
  • a heart rate that is consistently lower than 60 or above 100 beats per minute
  • reduced ability to exercise – your increased heart rate can make exercising difficult
  • chest discomfort – pain, pressure, or tightness in the chest
  • dizziness – when your heart beats more quickly than normal, your blood pressure can drop, and you may start to feel faint

Symptoms of atrial fibrillation are often classified by how long they last:

  • occasional symptoms come and go, may last for anything from a few minutes to several hours or days, could go away on their own, and may need treatment
  • persistent symptoms don’t go away on their own, and medications may be required to restore and retain a normal heart rhythm
  • long-standing persistent atrial fibrillation symptoms are continuous and last for longer than a year
  • permanent atrial fibrillation symptoms mean that a regular heart rhythm cannot be restored and that medications are required to prevent blood clots and control your heart rate

You should see your doctor if you experience any of the above symptoms.

What causes atrial fibrillation?

The heart is made up of chambers surrounded by muscular walls. There are two chambers at the bottom of the heart, called ventricles, and two at the top, called atria.

When the heart beats normally, the muscular walls of the atria and ventricles tighten and squeeze (contract) in turn, to push blood out of the heart and around the body. The muscular walls then relax to allow blood to fill the heart.

When you have atrial fibrillation, the atria (upper chambers) contract randomly and sometimes faster than normal. This means that your heart muscles can’t relax properly, reducing how well your heart can work.

Atrial fibrillation happens as a result of abnormal electrical impulses in your heart. When these start firing at random in the atria, this overrides your heart’s natural pacemaker, causing an irregular heart rhythm and pulse rate.

The exact cause of these abnormal electrical impulses remains unknown. But research shows that the chances of having the condition increase with age, typically affecting people aged over 65 most commonly. However, the condition can affect adults of any age.

Atrial fibrillation risk factors

Atrial fibrillation has several risk factors. These include:

You are also more likely to have atrial fibrillation if you have certain other medical conditions, such as:

  • high blood pressure
  • atherosclerosis (narrow arteries due to a build-up of fatty deposits)
  • heart disease
  • thyroid disease
  • heart valve problems
  • diabetes
  • lung disease
  • kidney disease
  • metabolic syndrome (a combination of diabetes, high blood pressure and obesity)
  • sleep apnoea (when breathing stops and starts in your sleep)

Complications of atrial fibrillation

Atrial fibrillation can cause complications, especially if the condition is not treated.

Atrial fibrillation’s chaotic heart rhythm can result in blood collection in the atria (upper chambers of the heart), forming blood clots. Blood clots in the left atrium (left upper chamber) can break free and travel to the brain, which can then cause a stroke.

You are also more likely to have a stroke from atrial fibrillation if you are older, have diabetes, have high blood pressure, have heart failure, or have a valvular disease (a disease involving one or more of the heart’s four valves).

Diagnosing atrial fibrillation

There are several tests available to diagnose atrial fibrillation. Initially, your doctor may examine you and ask various questions about your symptoms and medical history.

Standard tests that can help diagnose the condition include:

  • electrocardiogram (ECG) – an ECG detects whether your heart rhythm and its electrical activity (that stimulates heartbeats) is normal. It’s a pain-free test which takes approximately five minutes. During the test, small stickers called electrodes will be attached to your chest, arms and legs. These connect to the ECG machine using wires and record your heart’s electrical activity
  • echocardiogram – this is an ultrasound scan of your heart. An ultrasound is a procedure that uses high-frequency sound waves to develop a picture of your heart. It is used to check the structure of your heart and its valves, and whether it is functioning correctly
  • chest X-ray – sometimes, lung problems may cause atrial fibrillation. An X-ray of your chest may be used to check if that is the case.
  • blood tests – a range of blood tests can be used to determine underlying health conditions that may be behind the symptoms you are experiencing
  • holter monitor – a portable ECG device that is worn on your belt or carried in a pocket or shoulder strap. It can monitor your heart continuously during daily activities over a 24 hour – 7 day hour period
  • event recorder – a carriable monitor that is worn for much longer than a Holter monitor (usually two weeks). The wearer presses a button whenever they start to feel symptoms
  • stress test – this is a test done during exercise (or using a medication that mimics exercise) that can show how well your heart is working

Atrial fibrillation treatment

Treatment for atrial fibrillation will depend on the underlying cause and severity. However, the key treatment options available are detailed below.


Your doctor can prescribe blood-thinning medications called anticoagulants to help reduce your risk of a stroke, which is common with atrial fibrillation.

They may also prescribe medications that can help control your heart rate and return it to normal. These might include:

  • beta blockers
  • anti-arrhythmic medications
  • digoxin
  • calcium channel blockers

Cardioversion therapy

Cardioversion therapy is a procedure that involves shocking your heart to help return its rhythm to normal. It is normally carried out in a hospital to allow your healthcare team to keep a close eye on your heart until they feel it’s safe for you to return home.

The procedure can be done using two key methods: electrical cardioversion, which resets your heart rhythm by sending electrical shocks to the heart through electrodes, or drug cardioversion, which uses medications administered intravenously to reset your heart rhythm.

Catheter ablation

Catheter ablation involves very carefully destroying the diseased area of your heart that is responsible for the irregular electrical activity. It’s typically recommended if medication hasn’t worked for you or if you can’t tolerate it.

During the procedure, a catheter – a soft, thin wire – will be guided through one of your veins up to your heart where it will then be used to record electrical activity. Once the source of the abnormal electrical activity in your heart has been identified, a high-frequency radio wave will then be used to heat the diseased part of your heart and destroy the tissue.

The whole procedure normally takes between two and three hours to complete so you may be put to sleep using a general anaesthetic while it takes place. However, you should recover quickly and be able to carry out most of your normal activities the very next day.


Pacemakers are usually used to stop your heart from beating too slowly but they can also be used in cases of atrial fibrillation where there is a tendency for the heart to beat too slowly or in combination with a procedure that disconnects the top chambers from the bottom chambers of the heart.

A pacemaker is a small battery-operated device that is implanted surgically in your chest, just below your collarbone. Inserting it will involve a minor surgical procedure that can be carried out with local anaesthetic (numbing the area to be operated on) whilst you are awake.

Inserting a pacemaker is often recommended if your heart is no longer responding to medications, or if they are unsuitable for you to take. This is most common in people aged over 80.

Pacemakers help the heart to beat more regularly

Pacemakers can be used to help the heart beat more regularly.

How to prevent atrial fibrillation

Leading a healthy lifestyle can reduce the risk of heart disease and help prevent atrial fibrillation. Here are some top tips for maintaining a healthy heart:

  • quit smoking – lowers the risk of atherosclerosis (fat deposits in the arteries) and blood clots
  • exercise often – helps to prevent high blood pressure and maintain a healthy weight
  • eat a low-fat, low-salt diet – prepare meals rich in fruit, vegetables, and whole grains
  • manage stress – when you are stressed out or angry, heart rhythm problems can occur
  • limit alcohol or caffeine intake – or avoid them entirely

Discover our cardiology experts

Meet our team of cardiologists specialising in atrial fibrillation. Whether it’s maintaining heart health or implementing innovative interventions, our experts are here to offer personalised care tailored just for you.